A common ophthalmological surgical technique is the removal of a diseased or injured lens from the eye. Earlier techniques used for the removal of the lens typically is required a substantial incision to be made in the capsular bag in which the lens is encased. Such incisions were often on the order of 12 mm in length.
Later techniques focused on removing diseased lenses and inserting replacement artificial lenses through as small an incision as possible. For example, it is now a common technique to take an artificial intraocular lens (IOL), fold it and insert the folded lens through the incision, allowing the lens to unfold when it is properly positioned within the capsular bag. Similarly, efforts have been made to accomplish the removal of the diseased lens through an equally small incision.
One such removal technique is known as phacoemulsification. A typical phacoemulsification tool includes a handpiece to which is attached a hollow needle. Electrical energy is applied to a piezoelectric crystal to vibrate the needle at ultrasonic frequencies in order to fragment the diseased lens into small enough particles to be aspirated from the eye through the hollow needle. Commonly, an infusion sleeve is mounted around the needle to supply irrigating liquids to the eye in order to aid in flushing and aspirating the lens particles.
It is extremely important to properly infuse liquid during such surgery. Maintaining a sufficient amount of liquid prevents collapse of certain tissues within the eye and attendant injury or damage to delicate eye structures. As an example, endothelial cells can easily be damaged during such collapse and this damage is permanent because these cells do not regenerate. Some benefits of using as small incision as possible during such surgery are the minimization of leakage of liquid during and after surgery to help prevent tissue collapse, faster healing time and decreased post-operative astigmatism.
Phacoemulsification needles and tips are well represented in the prior art. Needles and tips of varying configurations are well known. A particular shape for a tip or needle is often dictated by the type of handpiece with which the needle is to be used.
U.S. Pat. No. 5,725,495 (Strukel et al) teaches and describes a phacoemulsification handpiece, sleeve and tip illustrating a wide variety of tip configurations and needle cross-sectional configurations.
U.S. Pat. No. 6,007,555 (Devine) teaches and describes an ultrasonic needle for surgical emulsification. The needle and its tip are shown in both circular and oval configurations.
U.S. Pat. No. 6,605,054 (Rockley) teaches and describes a multiple bypass port phacoemulsification tip having multiple aspiration ports and a single discharge port to infuse liquid into the eye.
U.S. Pat. No. 5,879,356 (Geuder) teaches and describes a surgical instrument for crushing crystalline eye lenses by means of ultrasound and for removing lens debris by suction which demonstrates the use of a sleeve positioned concentric to the needle and having a pair of discharge ports formed thereon.
U.S. Pat. No. 5,645,530 (Boukhny) teaches and describes a phacoemulsification sleeve, one variation of which has a bellows portion attached to a discharge port ring which directs an annular flow of liquid around the needle and into the eye. The use of the bellows is intended to, allow the sleeve to absorb spikes, in liquid pressure during the operation.
Published U.S. Patent Application No. 2003/0004455(Kadziauskas) teaches and describes a bi-manual phacoemulsification needle using separate emulsification and aspiration needles inserted into the eye simultaneously during surgery.
Published U.S. Patent Application No. 2006/0217672 (Chon) teaches and describes a phacoemulsification tip that is swaged or crimped at its distal end. The tip is intended for use with a handpiece producing torsional motion and the crimping forms cutting edges at the distal end.
Many phacoemulsification needles and tips are designed for use with handpieces that vibrate the needle longitudinally at relatively low frequencies. In addition to, longitudinal vibration, certain handpieces sold by Alcon, Inc. of Ft, Worth, Tex. claim to impart a torsional motion to the needle at an oscillation vibration frequency of about 100 cycles/second. There are also handpieces that provide torsional oscillation of the phacoemulsification tip at frequencies of about 32,000 cycles/second.
Use of the torsional-type, handpiece has called for phacoemulsification needle tip designs differing from those used with the longitudinal-type handpiece. For example, needles having been designed with tips that are shaped, swaged, and angled to take advantage of the needle motion created by the handpiece.
Many surgeons favor phacoemulsification needles having the straight tip design commonly used with longitudinal hand pieces. The great majority of surgeons use longitudinal handpieces rather than torsional hand pieces, often because torsional phacoemulsification equipment is more expensive than longitudinal equipment, and thus find themselves unable to take advantage of the enhanced phacoemulsification results claimed in torsional phaco.
Forming a needle tip in an off-axis position relative to the axis of the aspiration passageway extending through the needle body causes eccentric, motion or “wobble” during torsional phacoemulsification and improves the efficiency of phacoemulsification while retaining the straight-tip configuration. Surprisingly, I have also found that forming the tip in such an off-axis position also increases the efficiency of phacoemulsification when using a longitudinal hand piece. Preliminary clinical examinations indicate that using an off-axis needle with a longitudinal hand piece may be more efficient than using the same needle with a torsional hand piece providing 100% torsional action, where efficiency is measured by the energy dissipated during phacoemulsification. When used herein, the term “dissipated energy” refers to the amount of energy, most commonly measured in joules, used by the hand piece during phacoemulsification. Lower dissipated energy readings mean that less heat is being produced during phacoemulsification which lowers the possibility of thermal damage to the delicate eye tissues.
There are known phacoemulsification apparatus, such as the Infiniti® Vision System manufactured by Alcon Laboratories of Ft. Worth, Tex. which allow the surgeon to choose between using torsional motion, longitudinal motion, or a blend thereof in a single hand piece. A common blended setting uses, torsional motion two-thirds of the time, and longitudinal motion one-third of the time. It is believed that the “blended” motion produces a more three-dimensional effect because of the back-and-forth motion imparted during longitudinal phacoemulsification and the eccentric motion produced at the tip during torsional phaco.
Use of an off-axis tip with a longitudinal hand piece appears to create a hybrid type of phacoemulsification motion without using the more complex and expensive torsional phacoemulsification apparatus. I have also determined that the eccentric or wobble type of motion can be imparted to a phacoemulsification needle with no flare at the tip by forming the central aspiration passageway within the needle body in an off-axis position. It is also expected that similar results will be obtained using a straight phacoemulsification needle having an aspiration passageway that is formed with a cross sectional configuration different than the cross-section configuration of the needle body itself, and that these results will be further amplified if the passageway is also placed off-axis.
While the following describes a preferred embodiment or embodiments of the present invention, it is to be understood that such description is made by way of example only and is not intended to limit the scope of the present invention. It is expected that alterations and further modifications, as well as other and further applications of the principles of the present invention will occur to others skilled in the art to which the invention relates and, while differing from the foregoing, remain within the spirit and scope of the invention as herein described and claimed. Where means-plus-function clauses are used in the claims such language is intended to cover the structures described herein as performing the recited functions and not only structural equivalents but equivalent structures as well. For the purposes of the present disclosure, two structures that perform the same function within an environment described above may be equivalent structures.
I have determined that an eccentric or “wobble” motion can be imparted to a phacoemulsification needle by constructed the needle to include anomalies in distribution of the needle's mass. In other words, the needle is manufactured in a manner in which the distribution of mass about the needle's major axis is not uniform.
In accordance with the preferred embodiment of the present invention, the needle itself is formed with the central aspiration passageway angles with respect to the central axis of the needle body.
In another embodiment the needle with an angled aspiration passageway is combined with a flared tip that is centered on the needle body.
In another embodiment, an off-axis aspiration passageway is combined with a needle tip wherein the tip itself is formed with non-uniform distribution of mass.
In yet another embodiment, the needle tip having a non-uniform distribution of mass is combined with a passageway that is coaxial with axis of the needle body.
In another embodiment a bump or selected number of bumps is formed on the external surface of the needle tip to create a non-uniform distribution of mass.
In yet another embodiment the portion of the needle is formed from a metal having a first density while the remaining portion is formed from a metal having a different density.
In yet another embodiment, the portion of the needle is drilled away and the resulting aperture is plugged with a metallic plug having a density different than that of the density of the main needle body.
In another embodiment, a series of needle tips having non-uniform skewed ridges on double beveled needle tips.
In another embodiment, a portion of the needle body is formed with a diameter larger than the remaining portion.
In another embodiment, the distal portion of the needle body is formed a larger diameter, a larger portion of which is offset.